The present invention relates generally to the field of work machines, and more particularly, to control systems for use with work machines.
Many different types of work machines are manufactured that have tracks or wheels on each side of the machine that are independently controllable. Generally, an operator of such a machine is required to provide input through a joystick, steering wheel, or other operator input to control the speed of the tracks or wheels which thereby controls the speed and direction of movement of the machine. Many different applications require such machines to maintain a relatively constant heading and relatively constant speed. It would be preferable to have a system that automatically controls the speed of the tracks or wheels to help maintain the heading and speed of the machine.
One particular application where speed and heading are important is asphalt paving machines. Asphalt paving machines are used to spread asphalt relatively evenly over a desired surface. These machines are regularly used in the construction of roads, parking lots and other areas where a smooth durable surface is required for cars, trucks and other vehicles to travel. An asphalt paving machine generally includes a hopper for receiving asphalt material from a truck and a conveyor system for transferring the asphalt from the hopper for discharge on the roadbed. Screw augers spread the asphalt transversely across the road bed in front of a floating screed, which is connected to the paving machine by pivoting tow arms or draft arms. The screed smoothes and somewhat compacts the asphalt material and ideally leaves a roadbed of uniform depth and smoothness. The depth of the asphalt material is determined not only by the height of the screed, but also by the speed of the paving machine. If the machine is travelling too quickly, then less material will be laid on the roadbed and the depth will be thinner. If the paving machine is travelling slower, then more material will be laid on the roadbed and the depth will be thicker. Thus, it is preferable to have the paving machine travel at a uniform speed.
Because asphalt paving machines typically operate on roadbeds, in parking lots, and in other areas where the machine travels long straight paths laying the mat of material, it is sometimes tedious for the operator to make continual manual adjustments to the left and right track or wheel speeds to make sure that the paving machine is travelling straight and is maintaining a constant speed. Such manual adjustments will divert the operators attention away from other duties that could increase the quality of the paving job.
It would be preferable to have a control system that would cause a work machine to maintain a relatively constant heading while at the same time maintaining a relatively constant speed. The present invention is directed at overcoming one or more of the disadvantages associated with the prior art.
In one aspect of the present invention, a control system is provided that controls the direction of travel of work machines to maintain a desired heading and a desired speed. The control system preferably includes a first speed sensor associated with a left ground engaging propulsion mechanism and a second speed sensor associated with a right ground engaging propulsion mechanism. The speed sensors produce right and left speed signals which are then used by an electronic control module to produce control signals to control the speed of left and right hydraulic motor assembles, which thereby controls the heading and speed of the machines.
These and other aspects of the present invention will be apparent upon reading the following detailed description of the invention in connection with the drawings and appended claims.